In recent years, attempts to transplant various cells have been conducted in order to repair injured tissue. For instance, for repairing cardiac muscle tissue injured due to ischemic cardiopathy such as stenocardia and myocardial infarction, attempts have been made to utilize fetal cardiac muscle cells, skeletal myoblasts, mesenchymal stem cells, cardiac stem cells, and ES cells. (See Haraguchi et al., Stem Cells Transl Med. 2012 February; 1(2): 136-41).
As part of such attempts, cell structures formed by utilizing a scaffold and sheet-shaped cell cultures obtained by forming cells in a sheet shape have been developed (See JP-T-2007-528755).
In regard of application of a sheet-shaped cell culture to therapy, investigations of utilization of a cultured skin sheet for a skin injury due to burn or the like, utilization of a sheet-shaped cell culture of corneal epithelium for a corneal injury, utilization of a sheet-shaped cell culture of oral mucosa for endoscopic resection of esophageal cancer have been under way.
Cells to be used for cell transplantation are normally obtained by separating them from the subject's tissue relevant to the transplantation, in order to avoid adverse events such as rejection. In many cases, however, the tissue includes other cells than the target cells. If the cells obtained from the tissue are cultured without purification of the target cells, the other cells than the target cells are also proliferated, lowering the proportion of the target cells in the cells to be used for transplantation. However, when the other cells than the target cells are transplanted, a therapeutic effect as high as that in the case of transplantation of the target cells cannot be obtained. It may be impossible, therefore, to obtain a sufficient therapeutic effect even by transplanting the cells obtained from the tissue, if the cells to be transplanted are low in target cell purity.
As a measure to enhance the proportion of the target cells contained in a cell population separated from the tissue, there has been known, for example, a method wherein in separating skeletal myoblasts from a skeletal muscle tissue, the skeletal muscle tissue is subjected to an enzyme treatment by immersion in a proteinase solution for a predetermined time, the resulting enzyme treatment liquid is discarded, thereafter the skeletal muscle tissue is again subjected to an enzyme treatment by immersion in an proteinase solution for a predetermined time, and cells contained in the enzyme treatment liquid thus obtained are recovered (JP-A-2007-89442).